This invention relates to electric lamps and has particular reference to an improved lamp unit of compact size that employs a fluorescent lamp of convoluted configuration as the light source and is adapted for use in residential and commercial lighting fixtures which are designed for incandescent-type lamps.
Fluorescent lamp units that are specially constructed for use in conventional lighting fixtures having screw-type sockets are well known in the art. A lamp unit of this type having a triple-U-bent fluorescent lamp that is mounted on a base structure along with circuit means and is protected by a cover component which has one or more vent openings which cooperate with similar vent openings in the base structure to permit air to circulate through the lamp unit during operation and provide convection cooling is disclosed in U.S. Pat. No. 4,300,073 issued Nov. 10, 1981 to Henry Skwirut et al.
An air-cooled fluorescent lamp unit of the same type having an improved base member which is partitioned into two compartments to separate the ballast inductor from the ballast capacitor and thus facilitate cooling of these components by the circulating air flow is disclosed and claimed in U.S. Pat. No. 4,270,071 issued May 26, 1981 to Edward W. Morton.
It is also well known to provide a compact screw-in type fluorescent lamp unit with a base module that contains a miniaturized solid-state electronic circuit which permits the fluorescent lamp to be operated in a direct-current mode from an AC power source. A fluorescent lamp unit having such an integral DC-operating circuit is disclosed in U.S. Pat. No. 4,173,730 issued Nov. 6, 1979 to Robert G. Young et al.
Screw-in type lamp units having triple-U-bent lamp components that are protectively enclosed by covers of various shapes which are secured to base modules having a tapered portion are disclosed in U.S. Pat. No. Des. 262,406 issued Dec. 22, 1981 to Fritz E. Zabransky.
While the aforementioned pending Young, Skwirut et al., Morton et al. and Justice applications (together with U.S. Pat. Nos. 4,270,071 and 4,300,073) disclose various structural and circuit improvements for compact fluorescent lamp units, cooling of the convoluted discharge lamp and/or circuit components in each of the lamp units disclosed in such pending applications and prior patents is achieved by providing the cover and base module with one or more vent openings which cooperate with similar openings in the lamp-support structure or member within the housing in such a manner that air circulates through the entire lamp unit in a single flow pattern that traverses both of the compartments or chambers that are defined by the cover and base module. Hence, when such lamp units are burned in a "base-up" position, ambient air enters the vent openings in the protective cover, flows past the convoluted fluorescent lamp into the base module or structure which contains the circuit components and finally emerges from the unit through the vent openings in the base module or structure. If the prior art lamp units are burned in a "base-down" position, ambient air flows in a reverse direction and enters the unit through the vent openings in the base module, flows through the module compartment past the circuit components, up through the cover component past the discharge lamp and then out of the unit through the vent opening or openings in the top of the protective cover.
Hence, in each of the prior art lamp units the lamp-containing and circuit-containing compartments of the unit are interconnected and convection cooling is achieved by having the cool outside air circulate through the unit in a single flow pattern. While the resulting "uniflow" cooling concept is satisfactory and prevents the convoluted fluorescent lamp from overheating and exhibiting a characteristic drop in light output, it has been discovered that heat generated by the lamp is transferred into the base module under certain operating conditions with the result that the temperature within the module compartment is increased. This is particularly disadvantageous in the case of solid-state type electronic circuits of the kind disclosed and claimed in the aforementioned pending application Ser. No. 294,953 of Justice which employ components such as electrolytic capacitors, transistors and the like that are heat-sensitive and may fail if they become too hot.
The present invention overcomes these problems and disadvantages by providing a compact fluorescent lamp unit which is so constructed that air is directed through the lamp unit along two separate paths which produce flow patterns such that the discharge lamp that is located within the protective cover is air-cooled independently of the circuit components which are housed within the base module. This segregated or "dual-flow" mode of air-cooling the two main compartments of the lamp unit is achieved in accordance with a preferred embodiment by physically isolating and separating the lamp and circuit compartments from each other by an internal partition structure that extends laterally across the lamp unit at the point where the cover and base module interface with and are coupled to one another. The transverse partition structure is conformed to nest within the top portion of the base module and has a number of air ducts and recessed portions which cooperate with port openings and vents in the module walls to provide air passageways which direct ambient air through the lamp unit in two separate flow patterns--one which traverses the base module and another which allows air to circulate through the lamp compartment by means of a number of openings located around the periphery of the partition member and one or more vent openings in the top of the cover component. In addition to the "split-flow" patterns for the circulating air, the transverse partition structure is also so constructed that it serves as the support means for the convoluted fluorescent lamp and the circuit components which are located within the cover and base module, respectively.
Various alternative lamp unit embodiments which provide the desired "dual-flow" air paths by employing cover components and base modules of various shapes and construction in conjunction with an internal partition structure are also disclosed.